CSF Biomarkers of Parkinson Disease (PD) and Related Disorders: In 2012 we reported that synucleinopathies feature CSF neurochemical evidence for central dopamine (DA) and norepinephrine deficiency and that CSF 3,4-dihydroxyphenylacetic acid (DOPAC) provides a sensitive clinical laboratory means to identify PD even early in the disease (Goldstein et al., Brain 2012;135:1900-1913). For these findings to gain traction requires replication and extension of the findings in additional patient cohorts. Therefore, with approval of the NIH Office of Human Research Subjects Protections, we have established collaborations with P. Low (Mayo) and A. Stefani (Univ. of Tor Vergata, Rome, Italy), to receive and assayed CSF samples from patients with PD, MSA, progressive supranuclear palsy, or Alzheimers disease and control subjects. Preliminarily, the results confirm low CSF DOPAC in both PD and MSA. We also have requested CSF samples from the extramural NINDS PD Biomarkers Program. In the NINDS PDRisk study (NIH Clinical Protocol 09-N-0010) we are following people with multiple PD risk factors, to determine whether biomarkers of catecholamine deficiency, such as low CSF DOPAC, predicts later development of PD (see below). Since DOPAC undergoes substantial and individually variable metabolic conversion to homovanillic acid (HVA), we developed assay methodology for CSF HVA, with the prediction that combined measurement of HVA, DOPAC, and DA will refine CSF biomarkers of central DA deficiency in PD. Biomarkers of Risk of PD: We are testing whether people with multiple risk factors for PD (family history, loss of sense of smell, dream enactment behavior, orthostatic intolerance) have biomarkers of loss of catecholamine neurons in the brain or periphery and if so whether they develop clinical PD during follow-up. Via a unique Protocol-specific website (https://pdrisk.ninds.nih.gov) that has been visited by more than 85,000 people to date, more than 330 people have been identified with multiple statistical risk factors for PD. We are screening eligible people to confirm their risk factors, admitting them for inpatient biomarkers testing including autonomic function tests, brain 18F-DOPA PET, cardiac 18F-dopamine PET, and CSF catechols, and following them longitudinally over several years. We anticipate that accrual will be completed this year for at-risk participants. Baroreflex-sympathoneural dysfunction may be a sign of pre-motor PD, corresponding to medullary synucleinopathy. We reported a new method for quantitative assessment of baroreflex-sympathoneural function based on beat-to-beat blood pressure responses to the Valsalva maneuver (Rahman & Goldstein, 2014). We are applying this methodology in the PDRisk study. 11C-Methylreboxetine PET to Visualize Noradrenergic Innervation: Until recently, no radioligand for neuroimaging had successfully and specifically visualized central neural sites of noradrenergic innervation. 11C-Methylreboxetine (11C-MRB) has these capabilities. In conjunction with the NIH PET Department we introduced 11C-MRB PET scanning at the NIH Clinical Center and have begun to test patients with known or suspected central NE deficiency and control subjects. We are validating 11C-MRB as a selective ligand for the cell membrane NE transporter in humans by examining effects of NET blockade and are applying 11C-MRB scanning to test whether Lewy body diseases are associated with neuroimaging evidence of central noradrenergic denervation. Skin Biopsy Biomarkers of Synucleinopathies: In a collaborative study with R. Freeman (Harvard) as a member of the Autonomic Rare Diseases Clinical Research Consortium, we have provided skin biopsy specimens from patients with different forms of alpha-synucleinopathy, to determine whether alpha-synuclein or tyrosine hydroxylase immunostaining can provide pathophysiologically relevant biomarkers. With Abhik Ray-Chaudhury (SNB/DIR/ NINDS) we are developing methodology to detect DA-beta-hydroxylase in skin biopsy samples, as this should be an excellent biomarker of noradrenergic innervation.